In a vehicle equipped with an engine, as a transmission by which torque and rotational speed generated by the engine are appropriately transmitted to drive wheels according to the traveling condition of the vehicle, there is known to be an automatic transmission in which the gear ratio between the engine and the drive wheels is automatically set optimally.
Examples of automatic transmissions mounted in vehicles include a stepped automatic transmission in which multiple gear stages having different gear ratios are set using a planetary gear device and frictional engaging elements such as clutches and brakes, and a belt-type stepless transmission (continuously variable transmission (CVT)) in which the gear ratio is adjusted in a stepless manner.
In a vehicle equipped with a stepped automatic transmission, an electronic control unit (ECU) or the like stores a gear shift map that has gear shift lines (up-shift lines and down-shift lines) for obtaining an optimum gear stage according to the vehicle speed and accelerator opening degree (or throttle opening degree), and a gear stage is automatically set by calculating a target gear stage with reference to the gear shift map based on the vehicle speed and the accelerator opening degree, and engaging in a predetermined state or releasing clutches, brakes, a one-way clutch, or the like, which are frictional engaging elements, based on the target gear stage.
In a vehicle equipped with a stepped automatic transmission, a shift lever that is operated by a driver (user) is provided, and the shift position of the automatic transmission can be switched to a P position (parking range), an R position (reverse range), an N position (neutral range), a D position (drive range), and the like by operating the shift lever. Also, recent years have seen the practical use of automatic transmissions in which a manual gear shift mode (sequential mode) can be selected as well, and the gear stage (gear range) of the automatic transmission can be arbitrarily switched by a driver operation performed on the shift lever, a manual operation switch (e.g., a paddle switch), or the like (e.g., see PTL 1 and PTL 2).
Among vehicles equipped with a stepless transmission as well, there are vehicles in which in addition to an automatic gear shift mode in which the gear ratio of a stepless transmission is automatically switched according to the traveling condition of the vehicle, it is possible to select a manual gear shift mode in which the gear ratio of the stepless transmission is switched according to a driver operation performed on a shift lever, a manual operation switch, or the like.
With such a vehicle that can be switched between an automatic gear shift mode and a manual gear shift mode, sporty traveling with a sense of directness is possible in the manual gear shift mode, for example, by switching the chive force characteristics under the same conditions (same vehicle speed and same accelerator opening degree) in the automatic gear shift mode and the manual gear shift mode, for example.
Also, with a vehicle that can be switched between gear shift modes, when there is a switch from the automatic gear shift mode to the manual gear shift mode, the gear stage (gear ratio) that was selected in the automatic gear shift mode (D range) immediately previously to the operation for switching the gear shift mode is set as the initial gear stage (initial gear ratio) in the manual gear shift mode (M range) to which the gear shift mode is switched (conventional control). Also, when there is a switch from the manual gear shift mode (M range) to the automatic gear shift mode (D range), the initial gear stage (initial gear ratio) in the automatic gear shift mode (D range) to which the gear shift mode is switched is determined based on the gear shift lines of the aforementioned gear shift map (e.g., see FIG. 8).